Fluid metal electrical switch

ABSTRACT

A fluid metal electrical switch wherein the volume of fluid metal, which may engage or bridge complementary contacts, is confined in an elastomeric channel and a cam engaging and compressing the channel is provided with a recess defining the volume of fluid metal. Movement of the cam thereby moves the body of fluid metal to selected contact positions. The position of the fluid metal contact is therefore independent of position, orientation or acceleration of the device in which the switch is mounted.

1W mted States Patent 1 3,637,969 Vignini [4 1 Jan. 25, 1972 I 1 FLUID METAL ELECTRICAL SWITCH Primary Examinerl'lerman use Att0rney()strolenk, Faber, Gerb & Soffen [72] Inventor: Walter R. Vigninl, Peekskrll, NY.

[73] Assignee: Sonotone Corporation, Elmsford, NY.

22 F'l d: N 13 1970 1 e 57 ABSTRACT [21] Appl' 89,310 A fluid metal electrical switch wherein the volume of fluid metal, which may engage or bridge complementary contacts, [52] U.S. Cl ..-.....200/203, 200/211, 200/214 is confined in an elastomeric channel and a cam engaging and [5 1] Int. Cl. 4 ..H01h 29/00 cgmpressing the channel is provided with a recess defining the [58] Field of Search ..200/152 R, 152 K volume of fluid metal. Movement of the cam thereby moves the body of fluid metal to selected contact positions. The posi- [56] References Cited tion of the fluid metal contact is therefore independent of position, orientation or acceleration of the device in which the UNITED STATES PATENTS Switch is moumccL 3,358,l09 l2/l967 Schmid ..200/l52.9

5 Claims, 8 Drawing Figures FLUID METAL ELECTRICAL SWITCH The present invention'relates to switches and more particularly to an hermetically sealed multiposition switch of the fluid metal type, the operation of which is independent of the orientation of the switch. Therefore the switch will have particular fluid metal contact or bridging contact are well known. Such switches depend for their operation on a particular orientation and location of the switch with respect tothe center of the earth so that gravity will maintain the mercury body in a desired position. Where, however, the switch in use is subject to variations inorientation of the structure in.which it is mounted or is subject to acceleration, the utilization of any device which depends on gravity alone, to maintain the fluid mercury-body in a particular position is not indicated. Therefore, mercury switches have not heretofore been used in connection with devices that might be worn by an individual or with respect to devices which are subject to acceleration (except in those devices in which the mercury body is expected to respond to acceleration in a particular direction).

The present invention is therefore directed to a fluid metal or mercury switch in which the fluid mercury body is subject to control at all times in every contact position of the mercury body as well asthe off position. Essentially the invention requires that the mercury body be captured and held'in a channel or structure having at least one resilient wall and the provision of a cam structure which compresses the resilient wall over every'section thereof except the section which is fully filled bythefluid metal body; the movement of this cam structure to cause the uncompressed or unpressed section of the resilient wall 'to move in response to movement of the cam structure, will move the confined fluid metal body in accordance :with the movement of the cam structure. The path of movement of the fluid metalbody includes one or more contacts, preferably at least one pair of contacts which are to be bridged by the'fluidmetal body. i

I t will thus be clear that when the fluid metal body is caused tornove in the resilient wall panel by the rotation of the cam structure, the' fluidmetal body may move from aposition where itzhas no engagement with any contact to a position where it engages a single contact (in the case of the utilization of bridging contacts, this would still be an OFF position) to another position where it engages two aligned metal contacts,

thereby bridging themj itmay be moved to a thirdposition where it. engages the second contact and the third contact to bridge those two contacts and open the circuit between the first andsecond contacts, to further contact bridging positions if they are necessary, to anOFF position at the opposite end of its travel or to the original OFF position at the initial portion of its travel.

Appropriate detenting of the cam will provide appropriate settings for the position of the fluid metal body and appropriate markings on the cam or on the knob which rotates the cam will provide indications of the circuit position of the switch OFF," ON, or other positions.

In practice, the invention, as applied to a hearing aid structure of the present type, may have three contacts in the path of travel of the fluid metal body, arranged circularly with respect to a base. An elastomer material is secured adjacent the outer area of base annularly with respect to the base to form an arched annular channel over the contact. The fluid mercury is contained within this elastomer channel. The cam is secured so that it rotates concentrically with the channel and is appropriately pressed down on the base and on the channel so that a recess or opening in the cam defines the extent of the fluid metal body; that is, the elastomer material forming the channel is pressed down on the base by the cam except at that area where the cam is recessed or cut away.

The annular length of the recess or cutaway is arranged to match the volume of mercury included in the enclosed channel and to confine all of the mercury in the channel to the annular section defined by the recess or cutaway in the cam.

Consequently, as the cam is rotated in one direction, the two ends of the recess or cutaway of the cam move what is in effect an elongated bubble of mercury, from position to position by reason of the fact that the cam, during its rotation, progressively compresses the elastomer of the channel, and at the other end progressively releases the elastomer of the channel from compression.

By this means therefore, the fluid metal body is at all times confined within a clearly defined constant volume which, when the switch is set in a particular position, retains its orientation to the case and relationship to the contact carried thereby, and cannot be moved out of position by anyvariation in orientation or by any acceleration to which'the device in which the switch is located is subject.

The primary object of the present invention therefore is the provision of a switch having a movablefiuid metal body as a contacting element in which the fluid metal body is at all times confined in every position of the switch so that the fluid metal body cannot be moved with respect to the contact as a result of variation in orientation or acceleration of the device in which the'switch is mounted.

The foregoing and many'othe r objects of this invention will become apparent in the following description and drawings in which:

FIG. I is an expanded view of the elements of the novel fluid metal switch.

FIG. 2 is a cross-sectional view taken on line 2-2 of FIG. I, looking in the direction of the arrows.

FIG. 3 is a top plan view of the base and cam of the switch of FIGS. 1 and 2. J

FIG. 4 is a cross-sectional view corresponding to that of FIG. 2, showing an arrangement for the utilization of a pair of moving fluid metal bodies over individual annularly arranged lines of contacts. a

FIG. 5 is a cross-sectional view of a modified form of cam which may beutilized in connection with the contact arrangement ofFIG. 4. Y

FIG. 6,is a view corresponding to that of FIG. 3, showing the utilization of a plurality of fluid metal bodies as bridging contacts for multiple circuits.

FIG. 7 is a cross-sectional view of a cam which may cooperate with the contact base of FIG. 6. FIG. 8 is a view partly in perspective, showing a modified form of contact base with the polymer channel linearly arranged, and a slide cam member which will operate linearlyas a switch operator to move the fluid metal body from contact position to contact position.

Referring now to FIGS. 1, 2 and 3, the novel mercury switch comprises a base II on the upper surface I2 of which a plurality of contact elements 30 are annularly arranged. Since the operation of this switch is independent of orientation of the elastomeric material is annularly secured to the base II in a path which overlies the annularly arranged contacts 30 to form a continuous channel over the annular series of contacts and beyond. The elast meric housing may be a completely circular housing without any break or may be arranged to extend sufficiently beyond the contact at either end of the series to ensure that the enclosed fluid mercury body, I3, can be moved to a full OFF position at least at one end..A plate 22 is secured to the lower end of shaft 16 ill any suitable manner, as for instance, by the screw 23 and a compression spring 25 is captured between the plate 22 and the lower surface 14 of the base. This ensures that the cam element 17 will be drawn down towards the surface 12 and onto the elastomeric channel 20 with sufficient force to compress the elastomeric channel 20 as shown at the right side of FIG. 2.

The open space or recess 27 of the cam 17 is defined by the edges 28 and 29 thereof. The volume of mercury, 13, included in the channel formed by the elastomeric body 20 is sufficient to fill that portion of the channel 20 between the edges 28 and 29 of the cam 17. Consequently, as the knob 18 rotates the shaft 16 and the cam 17, the continued compression of the channel 20 at one end and release of the channel 20 at the other end will cause the mercury body, 13, to move annularly to various positions with respect to the contacts. When the edge 29 of the cam is at location 29a FIG. 3, the contact 300 is out of circuit and contacts 30b and 300 are bridged. When the cam edge 29 is at location 29b, contact 30c is out of the circuit and only contacts 30b and 30a are bridged. When the edge 29 of the cam 17 is at location 29 c, none of the contacts are bridged with any other and the switch is in the OFF position. When the edge 29 of the cam is at the location shown by the solid lines of FIG. 3, then contacts 30a, b, and c are bridged.

Thus, in a hearing aid, assuming that the microphone is connected when contact 30a and 30b are bridged, the setting for the cam for this purpose would be with the edge 29 of the cam 17 at location 29b. If another transducer or a telephone pickup is to be connected across contact 30b and 30c, then the setting of the cam so that the edge of the cam is at position 29a will effect this result and cut out the microphone. With the cam 17 set in the position shown by the solid lines of FIG. 3, both the microphone and the telephone pickup would be connected. With the cam set so that the edge 29 is at location 290, the switch will be in an OFF position with both the microphone and telephone pickup disconnected. Since contact 3012 can also be utilized to energize other circuits, then with the cam set so that the edge 29 is at location 29c, all other circuits will be OFF and the entire device will be OFF.

As will be clear from FIG. 2, the contacts 30 may be simple rivet-type structures, the head of which is countersunk in the case to be flush with the base and the leg 31 of which will pass through the base and be accessible for other connection.

Also, as shown in FIGS. 1 and 2, the cam structure may be detented to various positions corresponding to desired positions of the cam for desired circuit conditions. A plurality of recesses 40 in the base of the knob may be used, each corresponding to a different annular position of the cam 17 for a different circuit condition. A detent 41 may be mounted in vertical channel 42 of the base 11, biased outward toward the under surface of the cam 17 by compression spring 43 held in position by the screw 44 in channel 42. The recesses 40 are so arranged that on rotation of knob 18, the detent 41 may be cammed out of particular recess 40 and will then click into the next recess 40 on rotation of the knob 18 when that recess moves above the detent 41. This will provide a manual sensing of the individual positions of the contact operating member.

The material chosen for the elastomer body which forms the channel 20 and the material chosen for the cam 17 and particularly for the surface thereof, which compresses the channel 20, should be such that they may have appropriate low friction sliding engagement with each other. Since materials which are compatible in this manner are well known and capable of being supplied commercially, the specific material therefore forms no part of this invention. If desired, an appropriate lubricant may be placed between the under surface of cam 17 and the material which forms the channel 20.

An external indication of the particular setting of the switch may be provided by a marker 50 (FIG. 1) which cooperates which indicia on the surface of the housing 52 of the device in which the switch is mounted. In addition, or as a substitute, the cam itself may carry on its upper surface 53, appropriate indicia such as OFF, ON and cooperating with an opening 54 in the housing 52 to provide an indication of the contact position of the switch.

While the cam 17 has been shown as a discontinuous member with the ends 29 and 28 defining the extent and position of the mercury body, as shown in FIG. 5, the cam 117 may be annularly continuous and have recesses 127 (and 127a as hereinafter described) of the desired annular extent to define the mercury body. In the construction shown in FIG. 4, I have shown the cam 117 with two concentric recesses operating with two concentric channels 120a and 120b, each having its own set of contacts 113a and 113b, to provide for multiple circuit arrangements. The recesses 127 and 127a are individually arranged radially so that they may be congruent with each other or displaced radially with respect to each other and the rows of contacts 113a and 113b may be similarly arranged. This provides for a multiplicity of circuits and connections where the spacing of the contacts and the spacing of the recesses could be utilized to provide many switch positions (with appropriate detenting recesses of the type of detent 40 of FIG. 2), annularly arranged for the separate contact positions and with appropriate indicia on the upper surface of cam 53, cooperating with the opening 54 of housing wall 52 to provide appropriate indications of the circuit condition.

In FIG. 6 and 7, there is shown an alternate arrangement wherein separate mercury bodies 220a, 220b and 2206 may be utilized in connection with independent sets of contacts 213. In this case, the cam recess 227 of the cam 217 of FIG. 7 will be repeated for each desired mercury body as defined by the outline of each mercury body 220, so that each mercury body is used for only a single pair of contacts. A single channel may be used. Appropriate arrangement of the cam recesses to form the mercury bodies 220a, 220b and 220C and appropriate arrangements of the contacts 213 can then be utilized to effect different conditions of the circuits.

While the invention is directed to a mercury switch which operates regardless of orientation or acceleration. and which is particularly adapted for use in miniature applications such as, for instance, a hearing aid to be worn behind the ear or in the bow of eye glasses, it may, of course, have other applications. In such event, and for a particular application, it may be desirable to have a linear switch operator.

Accordingly, in FIG. 8, there is shown a modification of the invention in which the base 311 is a linear structure, the channel forming elastomer 320 is correspondingly linear and the contacts 313 are linearly arranged. The cam 317 in this case will constitute a flat member as shown, having the cam opening 327. The flat member 317 is pressed down on the upper surface 312 of the base 311 and has an operating extension 318 to move the flat member 317 linearly, to achieve the same successive result with respect to circuit correction as already described with respect to FIG. 1-7.

One method of obtaining the appropriate pressure of cam 317 against the channel 320 is indicated in FIG. 8. A plurality of legs 360 or a continuous wall, on one side, is provided for the cam element 317 connected to a parallel bottom wall 362 which captures a leaf spring 363 which engages the bottom wall of the base 311, thereby pulling the cam surface 317 down with predetermined pressure on the channel 320. The legs 331 of the contacts 313 may then be led out the side to clear the operating element of the cam 317.

In the foregoing, a fluid metal body switch has been described which is operative regardless of orientation or acceleration of the device in which the switch is mounted. The volume of mercury is at all times fully contained and restrained against displacement by variations in orientation or by variations in acceleration from the particular location at which the fluid body of mercury has been set. Since many variations and modifications of this invention will now be obvious to those skilled in the art, it is preferred that the scope of this invention be determined not by the specific disclosure herein contained but only by the appended claims.

Iclaim:

1. A fluid metal contact switch in which the volume and location of the body of fluid metal is independent of orientation, position and acceleration;

comprising a base, a plurality of contacts carried by said base;

an elastically compressible channel on said base and overlying said contacts;

the body of fluid metal being contained within said channel;

a cam member in engagement with the portion of said base carrying said channel;

said cam member compressing said channel against said base;

and a recess in said cam overlying said channel and defining a section of the channel not compressed by said cam;

said last mentioned uncompressed section of said channel confining and retaining said body of fluid metal;

said cam being movable along said base to vary the section of said channel which remains uncompressed and to move the fluid metal body in said channel as said uncompressed section of the channel varies continuously from one part of the channel to another;

the fluid metal being under continuous confinement and restraint in any position, orientation or acceleration of the switch.

2. The switch of claim 1 in which the contacts are circularly arranged on the base; the channel on the base overlying the contacts is annular and the cam is mounted to rotate about the center of the circular arrangement of contacts and the annular channel.

3. The switch of claim 2 in which the cam is secured to a rotatable shaft; and the shaft and base carry cooperating detent elements to provide settings of the contact positions of the switch.

4. The switch of claim 2 in which a plurality of concentric sets of circular arrangements of contacts are carried on said base; a corresponding plurality of channels each cooperates with each set of contacts; and the cam is provided with concentrically arranged recesses, each recess cooperating with a particular channel and a particular set of circularly arranged contacts.

5, The switch of claim 2 wherein the cam is provided with a plurality of recesses and a corresponding plurality of bodies of fluid metal are confined in the annular channel in sections defined by the separate recesses in the cam. 

1. A fluid metal contact switch in which the volume and location of the body of fluid metal is independent of orientation, position and acceleration; comprising a base, a plurality of contacts carried by said base; an elastically compressible channel on said base and overlying said contacts; the body of fluid metal being contained within said channel; a cam member in engagement with the portion of said base carrying said channel; said cam member compressing said channel against said base; and a recess in said cam overlying said channel and defining a section of the channel not compressed by said cam; said last mentioned uncompressed section of said channel confining and retaining said body of fluid metal; said cam being movable along said base to vary the section of said channel which remains uncompressed and to move the fluid metal body in said channel as said uncompressed section of the channel varies continuously from one part of the channel to another; the fluid metal being under continuous confinement and restraint in any position, orientation or acceleration of the switch.
 2. The switch of claim 1 in which the contacts are circularly arranged on the base; the channel on the base overlying the contacts is annular and the cam is mounted to rotate about the center of the circular arrangement of contacts and the annular channel.
 3. The switch of claim 2 in which the cam is secured to a rotatable shaft; and the shaft and base carry cooperating detent elements to provide settings of the contact positions of the switch.
 4. The switch of claim 2 in which a plurality of concentric sets of circular arrangements of contacts are carried on said base; a corresponding plurality of channels each cooperates with each set of contacts; and the cam is provided with concentrically arranged recesses, each recess cooperating with a particular channel and a particular set of circularly arranged contacts.
 5. The switch of claim 2 wherein the cam is Provided with a plurality of recesses and a corresponding plurality of bodies of fluid metal are confined in the annular channel in sections defined by the separate recesses in the cam. 